FIG. 19 shows a cooling member 607 formed by pressing a refrigerant introducing pipe 605 into a groove 603 of a heat-transfer member 601 and a punch 613 in which a pressing surface 611 is provided between two corners 609. The heat-transfer member 601 is an aluminum plate. The limit of a longitudinal direction in the groove 603 coincides with edges 615 of both sides of the heat-transfer member 601. The refrigerant introducing pipe 605 is a steel pipe. The cooling member 607 is assembled by the procedures mentioned below.
As shown in FIG. 20(a), the corners 609 of the punch 613 are positioned right above the edges 615 of the heat-transfer member 601 and the refrigerant introducing pipe 605 is inserted into the groove 603. At this point, as shown in 20(b), there is a clearance between an inner surface of the groove 603 and the refrigerant introducing pipe 605. Subsequently, the punch 613 is moved forward (fall) toward the groove 603 to press the pressing surface 611 of the punch 613 to the refrigerant introducing pipe 605. Thereby, as shown in FIGS. 20(c) and 20(d), the refrigerant introducing pipe 605 is plastically deformed and a joint between the heat-transfer member 601 and the refrigerant introducing pipe 605 at a place where the refrigerant introducing pipe 605 is closely fitted with the inner surface of the groove 603 is completed.
However, when the refrigerant introducing pipe 605 is pressed by the punch 13, scars 617 caused by the corners 609 remain on a surface of the refrigerant introducing pipe 605, resulting in damage in reliability of the refrigerant introducing pipe 605. When an external force is applied to the refrigerant introducing pipe 605 in a bending direction after the heat-transfer member 604 and the refrigerant introducing pipe 605 are joined, its stress focuses near a boundary between the refrigerant introducing pipe 605 and the edges 615, resulting in reduction in physical strength of the refrigerant introducing pipe 605. Although it is possible to avoid the focus of the aforementioned stress by performing R processing at the rim of the groove 603 so that clearance between the inner surface of the groove 603 and the refrigerant introducing pipe 605 may be formed near the edges 615, an extra processing expense for the processing is needed.
A reaction force created when the refrigerant introducing pipe 605 is pressed by the punch 613 allows the refrigerant introducing pipe 605 to bend toward the opposite side of the corners 609. This causes errors in dimension and direction of the refrigerant introducing pipe 605 projected from the edges 615 of the heat-transfer member 601. θ in FIG. 20(c) indicates an angle at which the refrigerant introducing pipe 605 is bent by the aforementioned reaction force.
Further, in the case where the refrigerant introducing pipe 605 is protected with a coating material after the assembling of the cooling member 607, the coating material is applied on a surface 619 of the heat-transfer member 601 and the refrigerant introducing pipe 605 and the coating material is further applied to the boundary between the refrigerant introducing pipe 605 projected from the edges 615 and the edges 615. The latter work is so troublesome that care should be taken to continue applying the coating material in the whole circumference of the refrigerant introducing pipe 605. In addition to that, technologies to fit metal pipes or the like into grooves are disclosed in JP 2007-218439 A, JP 2005-90794 A, and JP 10-79586 A.
In order to cool electric parts for producing heat such as power modules, it is designed that a refrigerant introducing pipe made of copper to which a refrigerant is introduced is inserted into a groove formed in an aluminum cooling member to make the cooling member in contact with the aforementioned electric parts. In this case, the refrigerant introducing pipe inserted into the groove of the cooling member is plastically deformed so as to be closely fitted with the groove of the cooling member with a press machine or the like, so that the refrigerant introducing pipe and the cooling member are joined.
However, when the refrigerant introducing pipe and the cooling member build up condensation at the time of cooling at lower temperatures than the atmosphere, corrosion of the refrigerant introducing pipe and the cooling member caused by moisture which gets into a joint (boundary) between the refrigerant introducing pipe and the cooling member becomes a problem. The aforementioned problem becomes prominent when poisonous gas which deteriorates metals is contained in the atmosphere or when poisonous gas or salt is dissolved in a dew condensation water under an environment of the splash of salt.
Further, in accordance with the progress of corrosion of the refrigerant introducing pipe and the cooling member, thermal resistance of the joint is increased, which leads to prevent the electric parts from being cooled. This deteriorates performance of the electric parts. Technologies related to a joint between a refrigerant introducing pipe and a cooling member are disclosed in JP 58-106395 A.
Moreover, technologies for bonding a pipe or the like to a groove of a heat-transfer member are disclosed in JP 2007-218439 A, JP 2005-90794 A, and JP 10-79586 A. As shown in FIG. 21(a), when manufacturing a cooling member formed by pressing a refrigerant introducing pipe into a groove of a heat-transfer member, a refrigerant introducing pipe 709 enters a groove 707 where an opening 705 is opened on a surface 703 of a heat-transfer member 701. Subsequently, the refrigerant introducing pipe 709 is pressed into the groove 707 with a punch 711 to plastically deform the refrigerant introducing pipe 709 so as to be closely fitted with an inner circumferential surface 713 of the groove 707 as shown in FIG. 21(b). This makes it possible to enlarge the width of the refrigerant introducing pipe 709 greater than a width A of the opening 705 to join the heat-transfer member 701 to the refrigerant introducing pipe 709.
The inner circumferential surface 713 of the opening 705 is in such a shape that the cross section in a width direction thereof is substantially arc-shaped. For instance, an external force in a deviation direction may be applied to the refrigerant introducing pipe 709. When the magnitude of this external force exceeds a friction force between the heat-transfer member 701 and the inner circumferential surface 713, such defects that the refrigerant introducing pipe 709 rotates relative to the heat-transfer member 701 occur. There is a limit to increase the aforementioned frictional force by simply increasing a force to press the refrigerant introducing pipe 709 with the punch 711.
It is preferable to increase an over hang quantity obtained by deducing the difference between the width A of the opening 705 and a full width B of the inner circumferential surface 713 to strengthen the join between the heat-transfer member 701 and the refrigerant introducing pipe 709 an that the refrigerant introducing pipe 709 plastically deformed as mentioned above may not be peeled off from the groove 707 of the heat-transfer member 701. However, to insert the refrigerant introducing pipe 709 into the groove 707 after passing through the opening 705, the width A of the opening 705 is needed to be greater than the diameter φ of the refrigerant introducing pipe 709. Accordingly, it is difficult to widen the difference between the width A and the full width B and the over hang quantity is limited. This causes a problem that it is impossible to strengthen the join between the heat-transfer member 701 and the refrigerant introducing pipe 709.
As shown in FIG. 22(a), a refrigerant introducing pipe 809 with diameter φ is inserted into a groove 807 where an opening 805 is opened on a surface 803 of a heat-transfer member 801 to press the refrigerant introducing pipe 809 into the groove 807 with a punch 811. This deforms the refrigerant introducing pipe 809 plastically so that the refrigerant introducing pipe 809 may be closely fitted with an inner circumferential surface of the groove 807 as shown in FIG. 22(b).
Since an outer circumference (π φ) of the refrigerant introducing pipe 809 and the circumference L of the groove 807 respectively include dimension errors, as shown in FIG. 22(c), there is a possibility that the refrigerant introducing pipe 809 is not closely fitted with the inner circumferential surface of the groove 807. AS a result, a clearance may remain between the refrigerant introducing pipe 809 and the groove 807. In this case, heat transfer from the heat-transfer member 801 to the refrigerant introducing pipe 809 is interfered. Further, when an external force is applied to the refrigerant introducing pipe 809 in a twisted direction, the refrigerant introducing pipe 809 has a problem with rotation relative to the heat-transfer member 801. Alternatively, as shown in FIG. 22(d), the refrigerant introducing pipe 809 forcibly pressed into the groove 807 may be bent in a concave shape. In this case, the cross-section area of the inner refrigerant introducing pipe 809 is becoming smaller, which results in interference of a flow of a refrigerant to be introduced to the refrigerant introducing pipe 809.
However, it is difficult to manage dimensions of the heat-transfer member 801 and the refrigerant introducing pipe 809 in an integrated fashion because the two respectively have a different manufacturing process, thereby it is inevitable to make the quality of the cooling member unstable.